Acetyl-l-carnitine (ALC) is the acetylated form of L-carnitine. It is responsible for the transport of long chain fatty acids into the mitochondria for use as fuel in aerobic respiration. Supplementation with Acetyl-L-Carnitine is believed to lead to enhanced fatty acid metabolism. Acetyl L Carnitine acts as a powerful antioxidant and is known to detoxify some of the waste products of metabolism including ammonia. It is has very similar metabolic effects as l-carnitine but has a greater level of bioavailability - it is transported more easily into the blood stream, passes more freely into the mitochondria, can cross the blood brain barrier and has a greater work rate than L-carnitine. Acetyl-l-carnitine is a naturally occuring substance that is found in small quantities in our diets, and is produced naturally in our body in small quantities. The human body is able to produce 20% of its L-carnitine needs from the essential amino acids methionine and lysine. Acetyl-L-Carnitine can be produced by the conversion of L-Carnitine and acetyl-CoA within the mitochondria. Acetyl-l-carnitine is required in larger amounts during prolonged exercise.

Who Should Consider Taking L Carnitine?

Acetyl-L-Carnitine has a number of benefits for anyone involved in intense or prolonged exercise. Anyone on a low calorie, who is vegetarian or on a low meat diet, or who trains intensively and for prolonged periods of timemay be prone to deficiencies in carnitine. L-Carnitine/Acetyl-L-carnitine is known to be important for endurance athletes as its main function is to transport fatty acids inside the mitochondria (energy powerhouses within muscle cells) where energy is produced aerobically by the oxidation of the fatty acids. However, Acetyl-L-Carnitne is believed to have greater bioavailability than non acetylated carnitine and passes more easily into the blood stream, and the mitochondria, where it has a greater work rate than L-carnitine. Research has also shown ALC to be more effective than L-carnitine (Hiat, 2004). Acetyl-L-Carnitine/l-carnitine supplementation is also believed to increase the use of fat for energy and therefore may be beneficial to people looking to loose weight. It has also been shown to have a number of health benefits.

Summary of Acetyl-L-Carnitine's Phyiological Effects:

Acetyl-L-Carnitine increases transport of fatty acids into the mitochondria for use in aerobic respiration

Improved blood flow and delivery of oxygen to working muscles

Acetyl-L-Carnitine reduces muscle damage and muscle soreness

Helps to improve the rate of recovery following strenuous exercise

Acetyl-L-Carnitine acts as a powerful antioxidant, and helps to detoxify the waste products of metabolism

Believed to enhance fat metabolism and may be beneficial for weight loss

Acetyl-L-Carnitine appears to have a positive effect on heart health and function, and has proved effective in the treatment of cardiac patients

Appears to be safe with no serious side effects

Acetyl-L-Carnitine Research

Acetyl-L-Carnitine, Heart Function, and Fatty Acid Transport

L-carnitine/Acetyl-l-carnitine plays a central role in lipid metabolism by transporting long chain fatty acids into the mitochondria for use as a fuel in aerobic metabolism. Dietary supplementation of L-carnitine is known to improve fat utilization (Ramsay 2000) and has a protective effect on the heart (Amin and Nagy, 2009; Loster et al., 1993; Malone et al., 2006;) and blood vessels (Hulsmann and Duebaar, 1988; Hiatt, 2004). Supplementation with L-Carnitine has even been shown to be beneficial to patients with chronic heart disease where it reduced the incidence of chronic heart failure and death (Iliceto et al., 1995). Carnitine supplementation can increase blood flow, and therefore enhance oxygen delivery, to the heart and working muscles (Kraemer and Volek, 2000). This effect is mainly attributable to carnitines ability to increase vasodilatation (Amin and Nagy 2009) which may be caused by an increased production of nitric oxide, and maintenance of existing nitric oxide by acetyl-l-carnitine (Bloomer 2009). Acetyl-l-carnitines ability to improved blood supply during exercise may enhance exercise performance, improvements in blood supply may also enhance post exercise recovery.

Acetyl-L-Carnitine/l-carnitine is known to have good antioxidant activity (Amin and Nagy, 2009; Gülçin I. 2006) and has the ability to detoxify ammonia, a metabolic by-product associated with early fatigue (Kanter and Williams, 1995). The ability of acety-l-carnitine to detoxify metabolic waste products and protect against the cell damaging effects of free-radicals may contribute to the beneficial effects seen when ALC is taken by endurance athletes.

Research shows that carnitine levels can fall dramatically with exercise (Hiatt et al 1989) and as such L-carnitine has become a popular supplement for endurance athletes during periods of intense training (Neumann et al., 2000). Research has shown that supplementing with 1g of carnitine a day can help to protect against reductions in muscle carnitine levels during periods of increased training volume or increased intensity (Giamberardino et al., 1996). Improved recovery following L-carnitine supplementation is also supported by Volek et al., 2002, who demonstrated reduced: markers of muscle damage, reduced tissue damage, reduced muscle soreness as well as reduced levels of free radical damage. Supplementation of 2g of L-Carnitine has been demonstrated to reduce levels of muscle damage (Jeff et al 2002; Kraemer et al., 2003). Both of these research teams suggested that Carnitine supplementation may be particularly effective at improving the rate of recovery. There appears to be very clear evidence that L-carnitine supplementation has beneficial effects on training, competition, and recovery from strenuous training (Karlic and Lohminger, 2004). In this way Acetyl-L-Carnitine helps athletes to tolerate greater training loads, and therefore gives athletes the potential to train at higher levels with a reduced risk of overtraining.

One particularly promising aspect of L-carnitine supplementation is that it may have a long term positive effect that lasts beyond the supplementation period. Research looking at the positive effects of L-carnitine supplementation on cardiac patients found that exercise performance was still improved 60 days after supplementation was stopped (Loster et al., 1999). Therefore, you may still get a positive benefit from L-carnitine even when you have stopped taking it.

Acetyl-L-Carnitine and Testosterone Levels

As well as producing all of the physiological benefits described above, Acetyl-L-Carnitine has some additional benefits that won’t occur with plain L-carnitine supplemetation. Bidzinska et al., 1993, demonstrated that Acetyl-L-Carnitine supplementation helps to prevent a drop in testosterone production following periods of physical or mental stress. Further studies (Krsmanovic et al., 1994) have also demonstrated that Acetyl-L-Carnitine supplementation promotes the growth and activity of cells in the brain responsible for producing hormones that activate testosterone production. Acetyl-L-Carnitine may therefore help athletes to cope more effectively with the high levels of physical and mental stress associated with large training volumes.

Is Acetyl-L-Carnitine effective?

Acetyl-L-Carnitine appears to be effective at enhancing the rate of recovery from exercise, reducing muscle soreness, improving heart function, enhancing brain function, and speeding up the transport of fatty acids into the mitochondria.

How to take Acetyl-L-Carnitine?

The general recommendation for acetyl-l-carnitine/l-carnitine supplementation is 1-2g per day during periods of intensified training (Neumann et al., 2000). It is generally recommended that this is taken on an empty stomach in the morning or early afternoon – try not to take Acetyl-L-Carnitine too late in the evening as it may make you feel more alert and therefore make it harder to sleep. High doseages should be avoided as the excess is likely to be excreted and therefore wasted. When training load is reduced, acetyl-l-carnitine/L-carnitine intake should be stopped. This is important, particularly when taking larger doses as it helps to ensure that the body's own production of acetyl-l-carnitine/L-carnitine is not disrupted and remains active.

For general health benefits it is normally recommended to take 250mg-1,000mg daily of Acetyl-L-Carnitine.

There is insufficient evidence to provide recommendations for the best dose of ALC for weight management/weight loss, however it most commonly taken at between 1,000mg-3,000mg daily in divided doses.

Acetyl-L-Carnitine Side Effects

Acetyl-L-Carnitine/L-Carnitine is non-toxic and appears to be free of side effects when taken at doses of up to 6g daily.